It is well known that preheating the fuel used in an internal combustion engine improves the efficiency of the engine. Further, preheating the fuel typically used in a diesel engine can avoid serious fuel flow problems well known to occur in cold weather environments.
Diesel fuel, and in particular the No. 2 fuel oil typically burned by the engines of today's over-the-road trucks, can congeal or "wax" in the cold weather regularly experienced during the winter months in the northern states of the United States and in Canada. The jelling or "waxing" of fuel can shut a diesel engine down, necessitating the towing of the vehicle to a repair facility where the fuel tank must be heated to alleviate the problem. The expense of towing and downtime can be substantial.
A number of methods and devices have been developed in an attempt to solve the problem of the congealing of fuel oil in cold weather. One method has been to install a heater in the fuel line. U.S. Pat. No. 3,929,187 discloses a device which utilizes this method. However, this method does not solve the problem of the fuel oil's congealing within the fuel tank before it even gets into the fuel line.
Another method is to install a heater in the fuel tank. U.S. Pat. No. 4,237,850 discloses a device which utilizes this second method. The device disclosed in this patent has two primary disadvantages. One, while the fuel can be heated in the tank to a temperature above that at which it "waxes", it is not necessarily heated to a temperature which will prevent it from congealing in the fuel line in extremely cold weather, because of the volume of fuel which must be heated in the tank which is usually directly exposed to the cold outside air temperatures. Two, the device disclosed in this patent requires an access opening which must be cut/formed into the top of the fuel tank prior to installation of the device.
Therefore, it is a principal object of the present invention to provide a system for preheating diesel fuel, both in the fuel tank and in the fuel supply line between the tank and the engine, to a temperature above that at which the fuel would normally congeal.
It is a further object of the present invention to provide a system for preheating the diesel fuel leaving both the fuel tank and the in-line heater to a temperature which is sufficiently higher than the temperature at which the fuel would normally congeal such that the fuel cannot jell at any point in the fuel line between the fuel tank and the diesel engine to which it is supplied.
It is yet another object of the present invention to provide a system for preheating the fuel in the fuel tank of a diesel engine-powered vehicle or machine which includes a heat exchanger which can be installed through and secured in the opening normally provided in such a fuel tank for the installation of a fuel level gauge.
It is a still further object of the present invention to provide a diesel fuel supply line heater to be mounted in series with the fuel supply line between the engine and the tank to provide in-line as well as in-tank fuel heating.
It is yet a further object of the present invention to provide an in-line heater which can use fuel returned from the engine as the heated liquid in the tank heater and eliminate the possibility of contaminating the fuel in the tank by a foreign liquid should leakage occur.
It is another object of the present invention to utilize the heat inherent in the unused fuel being returned from the engine to aid in heating the fuel in the in-line heater.
It is another object of the present invention to heat still further the unused fuel being returned from the engine so that it can be used to aid in heating the fuel in the remainder of the system.
It is yet another object of the present invention to provide such an in-line heater having a water drain petcock so as to drain out any water introduced into the fuel by condensation, thus eliminating another possible source of fuel line freezing, as well as contamination.
Finally, it is yet one more object of the present invention to provide such an in-line heater having a capped filler spout input means for introducing a quantity of diesel fuel for beginning the process (priming) at initial installation and at other times as may be desired.